JavaScript Tutorials

JavaScript Array keys()
Syntax & Examples

Array.keys() method

The keys() method of the Array class in JavaScript returns a new array iterator that contains the keys for each index in the calling array.

Syntax of Array.keys()

The syntax of Array.keys() method is:

keys()

This keys() method of Array returns a new array iterator that contains the keys for each index in the calling array.

Return Type

Array.keys() returns value of type Iterator.


✐ Examples

1 Using keys() method to iterate over keys

In JavaScript, we can use the keys() method to iterate over keys in an array.

For example,

  1. We define an array variable arr with elements ['apple', 'banana', 'cherry'].
  2. We create an iterator using the keys() method on arr.
  3. We use a for...of loop to iterate over each key in the iterator.
  4. Inside the loop, we log each key to the console.

JavaScript Program

const arr = ['apple', 'banana', 'cherry'];
const iterator = arr.keys();
for (const key of iterator) {
  console.log(key);
}

Output

0
1
2

2 Using keys() method with destructuring

We can use destructuring with keys() method to extract keys from the iterator.

For example,

  1. We define an array variable arr with elements ['apple', 'banana', 'cherry'].
  2. We create an iterator using the keys() method on arr.
  3. We use destructuring to extract keys from the iterator in a for...of loop.
  4. Inside the loop, we log key to the console.

JavaScript Program

const arr = ['apple', 'banana', 'cherry'];
const iterator = arr.keys();
for (const key of iterator) {
  console.log(`Key: ${key}`);
}

Output

Key: 0
Key: 1
Key: 2

Summary

In this JavaScript tutorial, we learned about keys() method of Array: the syntax and few working examples with output and detailed explanation for each example.